The latest official results released on Tuesday morning, with nearly 97 percent of the votes from Sunday’s runoff now counted, gave Kuczynski 50.15 percent of the vote. That’s just 0.3 points, and about 50,000 votes, more than the former congresswoman.

The electoral authorities said the very last results may not trickle in until the end of the week. Though these primarily come from pro-Fujimori poor rural areas, and foreign embassies, pollsters have said it is unlikely that the outcome could be reversed.

Kuczynski razor-think lead comes from having ridden a late-breaking wave of powerful anti-Fujimorista sentiment with many Peruvians fearful that Keiko, as she is usually known in Peru, would take the Andean nation back to the dark days when her father oversaw a rampant kleptocracy and serious human rights abuses.

The former president is now serving a 25-year jail term for directing death squads and manipulating the media against his critics.

Running on a populist right-wing platform emphasizing a military crackdown on violent crime, Keiko received 40 percent support in the first round vote on April 10, double Kuczynski’s tally. Just a week ago, polls showed Kuczynski still five points or more behind.

Yet he managed to turn that around despite a background on Wall Street that made him more at home in the board room than schmoozing voters in Peru’s grittier neighborhoods. Despite a common perception of all Peruvian politicians as corrupt, Kuczynski has also avoided ever being seriously linked to allegations of graft.

Educated at Oxford and Princeton, the 77-year-old economist with a Swiss mother and Polish father carved out a diverse career involving top jobs at the World Bank and the IMF. He has also served as Peru’s economy minister and, in 2005-2006 under centrist president Alejandro Toledo, as prime minister.

His wonky and foreign pedigree made Kuczynski vulnerable to campaign claims by his opponents that he represented Lima’s largely-white elite, hopelessly out of touch with Peru’s poor majority.

Kuczynski also made his own gaffes.

He reluctantly renounced his dual US citizenship at the start of the campaign. Keiko’s supporters labeled him el gringo — a nickname no Latin American politician wants to be burdened with.

On the campaign trail, he also allowed himself to be caught on camera as he dropped his pants to try on a swimming suit in a street market.

Possibly showing the effect of months of campaigning across Peru’s rugged national territory, Kuczynski also made a potentially fatal strategic error in calling young leftist congresswoman Veronika Mendoza “a half-red who hasn’t done anything with her dog’s life.” He then narrowly beat her into second place in April’s first round to win his place in Sunday’s runoff.

Mendoza’s subsequent decision to urge her supporters to vote for Kuczynski to save Peruvian democracy, is being viewed as decisive in the his late surge.

“She [Keiko] has proven that she is gravely compromised by corruption, the mafia and drug trafficking,” Mendoza said in a YouTube video that went viral.

Kuczynski also benefitted from fresh corruption scandals that have engulfed two senior members of Keiko’s Popular Force party.

Those scandals include the revelation that Popular Force’s general secretary, and principal funder, is being investigated by the US Drug Enforcement Administration, as well as a subsequent attempt by Keiko’s vice presidential candidate to discredit the DEA informant with a doctored audio recording.

According to Alfredo Torres, head of the polling company Ipsos Peru, these scandals left “an ugly feeling” for many voters.

“Keiko paid for the series of incredible blunders and scandals of the last couple of weeks,” added Steven Levitsky, a Harvard political scientist who pens a column in Peruvian newspaper La República. “It reversed all her efforts over the last five years to distance Fujimorismo from exactly those kind of bad memories of the 1990s. We are seeing just how hard it is to repackage a political movement as corrupt and criminal as Fujimorismo.”

The shock result also raises questions about the future of Fujimorismo.

The party won a narrow overall majority in Peru’s 130-member congress during the April 10 election, but Levitsky expects that this could fall apart if Kuczynski does win Sunday’s election and Keiko reacts to her second failure to win the presidency by walking away.

“Many of them just jumped on the bandwagon because they saw an opportunity to get into congress,” Levitsky said of the new deputies. “They are not necessarily committed, die-hard party members.”

Related: Peruvian Activists Predict a Right-Wing President Will Bring More Conflict Over Mines

Fujimori’s Popular Force party shares Kuczynski’s commitment to continue the free-market policies that have coincided with one of Latin America’s strongest booms since the turn of the millennium.

But with just 18 members of congress from his Peruvians for Change party, he could find his plans for sweeping reforms of the country’s corruption-plagued and inefficient institutions blocked entirely if he does become president.

“They called us drug traffickers and thieves,” Fujimorista congresswoman Lourdes Alcorta told the Associated Press. “It’s going to be difficult for us to hug them.”

Marina Navarro, head of Amnesty International’s Peru branch, called on Kuczynski to address the many unresolved human rights legacy issues left by Alberto Fujimori’s 1990-2000 presidency, including finally providing compensation to the thousands of victims of forced sterilizations under a notorious population control program.

She also said she hoped that Peru had averted a drastic worsening of violent crime and human rights abuses, which she says would be triggered by the implementation of Keiko’s plans to use the military to tackle crime.

“It has been disastrous in Mexico, Honduras and El Salvador,” Navarro said, of the drastic crackdowns that have sparked escalations of the violence in other Latin American countries. “It would have been the same here.”